Dental trays are receptacles that are used to carry a medicine or dental hygiene materials, such as bleaching agents or fluoride application, and apply them to the teeth. It confines the material next to the teeth during the application.
The invention disclosed in U.S. Pat. No. 5,076,791, uses ethylene vinyl acetate and creates a customized dental tray. The resultant tray is so thick that it may cause discomfort. Additionally, it is not hard at normal temperatures and gives less than a custom fit.
Finally, U.S. Pat. No. 5,616,027 discloses a hard, thin dental tray, suitable for many types of dental and at home procedures and uses. The patent uses ethylene vinyl acetate for an outer, non-impression forming tray that can be softened using boiling water. The thin inner tray is customizable to the same accuracy as more expensive custom trays created on a model, but at a fraction of the cost in time, professional expertise or equipment. The inner tray is principally made of a composition of polycaprolactone polymer with co-polymers and additives. The thin dental trays can be customized and molded in the home or outside of a dental office. The problem with this prior art tray and all the others of similar design is that it uses a polymer that can not be shaped at warm temperatures but requires higher temperatures to form, such as when the tray is heated in boiling water.
Since the early 1960s, there have been trays formable by the use of boiling water, which is far too hot for use with a patient. When the tray cools to a usable temperature, the window of pliability and comfort is so small that either the patient experiences discomfort or a bad fit is achieved.
Another industry where hot melting of thermoplastics is the athletic mouthguard industry. U.S. Pat. No. 3,312,218 teaches a protective mouthpiece that can be softened with boiling or near boiling water, then cooled to a temperature and formed in situ by the user. It has been found that a person normally can tolerate a thermoplastic at a temperature of less than 160° F. With a mouthguard, the fit is not as critical as it is with a dental tray but there is another important difference between mouthguards and dental trays. Specifically, mouthguards are thick and hold the heat longer, allowing the user to adjust the shape and fit over a longer period of time than is possible with the thinner and therefore faster cooling dental trays. Thus the window of time and temperature is much smaller for dental trays.
At the present time, the only available dental trays are those which include a front wall and a back wall, with a horseshoe or U-shaped trough in which the treating agent is placed. These two-wall trays are limited in length and wall height because of the requirements when placing the tray in a patient's mouth.
One embodiment of the present invention is the formation of a dental tray that has only one outer labial front wall, thus permitting it to be inserted into a patient's mouth without the obstruction of an inner (lingual) wall.
Another embodiment is to provide a flexible joint on the bottom or planar portion of the tray that can be raised or lifted by the patient, preferably using its tongue, to form an inner (lingual) wall after insertion.
Other embodiments will appear hereinafter.